Refrigerating cycle device

ABSTRACT

Provided is a refrigerating cycle apparatus in which, even if large power is required to start up an expander, the expander may be started up by activating a compressor. An air conditioner including a first compressor for compressing a refrigerant, an outdoor heat exchanger for radiating heat of the refrigerant compressed by the first compressor, an expander for decompressing the refrigerant that has passed through the outdoor heat exchanger, an indoor heat exchanger in which the refrigerant decompressed by the expander is evaporated, and a drive shaft for recovering power that is generated when the refrigerant is decompressed by the expander includes an on-off valve which is provided between the expander and the indoor heat exchanger and controls movement of the refrigerant from the expander to the indoor heat exchanger. After the first compressor is started up to increase a pressure of the refrigerant in the expander to a critical pressure or higher, the on-off valve is opened and the expander is started up by a dynamic pressure of the refrigerant.

TECHNICAL FIELD

The present invention relates to a refrigerating cycle apparatusincluding a power recovery device for recovering power that is generatedwhen a refrigerant is decompressed by an expander.

BACKGROUND ART

Conventionally, there is known a refrigerating cycle apparatus includinga first compressor for compressing a refrigerant, a radiator forradiating heat of the refrigerant compressed by the first compressor, anexpander for decompressing the refrigerant that has passed through theradiator, an evaporator in which the refrigerant decompressed by theexpander is evaporated, and a power generator which is connected to theexpander, recovers power that is generated when the refrigerant isdecompressed by the expander, and converts the power into electricity(see, for example, Patent Document 1).

There is also known a refrigerating cycle apparatus further including asecond compressor which is provided to the expander and utilizes thepower recovered from the expander.

Patent Document 1: JP 2006-132818 A

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, in the above-mentioned cases, when the refrigerating cycleapparatus has been in an inactive state for a longtime, for example,refrigerator oil in the expander is increased in viscosity due to lowtemperature so that large power is required to start up the expander.Therefore, there has been a problem in that, even when the firstcompressor is started up, the expander may not be able to be started up.

There has been another problem in that, when foreign particles enterfrom an inlet of the refrigerant of the expander or the secondcompressor and caught up in a rotating part therein, the operationcontinues under inertia of the rotating part in a steady operatingstate, but the expander stops in a start-up operating state becausethere is no inertia of the rotating part.

The present invention has been made to solve the above-mentionedproblems, and an object of the present invention is therefore to providea refrigerating cycle apparatus in which, even if large power isrequired to start up an expander, the expander may be started up byactivating a first compressor.

Means for Solving the Problems

The present invention provides a refrigerating cycle apparatusincluding: a first compressor for compressing a refrigerant; a radiatorfor radiating heat of the refrigerant compressed by the firstcompressor; an expander for decompressing the refrigerant that haspassed through the radiator; an evaporator in which the refrigerantdecompressed by the expander is evaporated; and a power recovery devicewhich is connected to the expander and recovers power that is generatedwhen the refrigerant is decompressed by the expander, the refrigeratingcycle apparatus including refrigerant movement control means which isprovided in a channel of the refrigerant from the expander to theevaporator and controls a flow rate of the refrigerant moving from theexpander to the evaporator, in which, after the first compressor isstarted up to increase a pressure of the refrigerant in the expander,the refrigerant movement control means controls the flow rate of therefrigerant to start up the expander by a dynamic pressure of therefrigerant.

EFFECTS OF THE INVENTION

According to the refrigerating cycle apparatus of the present invention,even if large power is required to start up the expander, the firstcompressor is started up to increase the pressure of the refrigerant inthe expander, and then the refrigerant movement control means controlsthe flow rate of the refrigerant so that the expander may be started upby the dynamic pressure of the refrigerant.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] A refrigerant circuit diagram in cooling operation of an airconditioner according to a first embodiment of the present invention.

[FIG. 2] A refrigerant circuit diagram in heating operation of the airconditioner of FIG. 1.

[FIG. 3] FIG. 3( a) is a schematic diagram illustrating a breakdown ofpower transferred from an expander to a second compressor in a steadystate, and FIG. 3( b) is a schematic diagram illustrating a breakdown ofthe power transferred from the expander to the second compressor duringactivation.

[FIG. 4] FIG. 4( a) is a diagram illustrating a pressure of arefrigerant, a volume of the refrigerant, and a mass of the refrigerantin the steady state of the expander, and FIG. 4( b) is a diagramillustrating the pressure of the refrigerant, the volume of therefrigerant, and the mass of the refrigerant during the activation ofthe expander.

[FIG. 5] A flow chart illustrating start-up operation of the airconditioner of FIGS. 1 and 2.

[FIG. 6] A refrigerant circuit diagram of the air conditioner in asecond start-up mode.

[FIG. 7] A refrigerant circuit diagram of a water heater according to asecond embodiment of the present invention.

[FIG. 8] A flow chart illustrating start-up operation of the waterheater of FIG. 7.

[FIG. 9] A refrigerant circuit diagram of a water heater according to athird embodiment of the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention are described withreference to drawings. Throughout the drawings, the same referencesymbols are assigned to the same or like members and parts fordescription.

First Embodiment

FIG. 1 is a refrigerant circuit diagram in cooling operation of an airconditioner according to a first embodiment of the present invention,and FIG. 2 is a refrigerant circuit diagram in heating operation of theair conditioner of FIG. 1.

The air conditioner, which is a refrigerating cycle apparatus accordingto this embodiment, includes a first compressor 1 for compressing arefrigerant, an outdoor heat exchanger 2 which serves as a radiator inwhich the refrigerant radiates heat in the cooling operation and as anevaporator in which the refrigerant is evaporated in the heatingoperation, an expander 3 for decompressing the refrigerant passingtherethrough, an indoor heat exchanger 4 which serves as an evaporatorin which the refrigerant is evaporated in the cooling operation and as aradiator in which the refrigerant radiates heat in the heatingoperation, and a drive shaft 5 which is connected to the expander 3 andserves as a power recovery device for recovering power that is generatedwhen the refrigerant is decompressed by the expander 3.

The air conditioner also includes an on-off valve 6 which is provideddownstream of the expander 3 and serves as refrigerant movement controlmeans that is fully closed to restrict movement of the refrigerant fromthe expander 3 to the downstream side and is fully opened to control aflow rate of the refrigerant moving from the expander 3 to thedownstream side.

Further, the air conditioner uses carbon dioxide as the refrigerant. Thecarbon dioxide refrigerant has an ozone depletion potential of zero anda smaller global warming potential compared to the conventionalfluorocarbon refrigerant.

The outdoor heat exchanger 2 includes a first outdoor heat exchangerportion 2 a and a second outdoor heat exchanger portion 2 b. In achannel of the refrigerant between the first outdoor heat exchangerportion 2 a and the second outdoor heat exchanger portion 2 b, there areprovided a switch 7 a and a switch 7 b which are closed in the coolingoperation to block the refrigerant and opened in the heating operationto allow the refrigerant to pass therethrough.

Therefore, the first outdoor heat exchanger portion 2 a and the secondoutdoor heat exchanger portion 2 b are configured so that the firstoutdoor heat exchanger portion 2 a and the second outdoor heat exchangerportion 2 b are connected in series in the cooling operation and thefirst outdoor heat exchanger portion 2 a and the second outdoor heatexchanger portion 2 b are connected in parallel in the heatingoperation.

The indoor heat exchanger 4 includes a first indoor heat exchangerportion 4 a and a second indoor heat exchanger portion 4 b, and thefirst indoor heat exchanger portion 4 a and the second indoor heatexchanger portion 4 b are connected in parallel.

The first indoor heat exchanger portion 4 a is connected to an indoorexpansion valve 8 a, and the second indoor heat exchanger portion 4 b isconnected to an indoor expansion valve 8 b.

Therefore, the refrigerant is decompressed in the cooling operation sothat the refrigerant may be evaporated in the first indoor heatexchanger portion 4 a and the second indoor heat exchanger portion 4 b,and the refrigerant is decompressed in the heating operation so that therefrigerant, which has radiated heat in the first indoor heat exchangerportion 4 a and the second indoor heat exchanger portion 4 b, may beevaporated in the first outdoor heat exchanger portion 2 a and thesecond outdoor heat exchanger portion 2 b.

In the channel of the refrigerant between the first outdoor heatexchanger portion 2 a and the second outdoor heat exchanger portion 2 b,there is provided a second compressor 9 for compressing the refrigerantthat has passed through the first outdoor heat exchanger portion 2 a inthe cooling operation.

The second compressor 9 is connected to the expander 3 through the driveshaft 5, and hence the power generated in the expander 3 is recovered bythe drive shaft 5 and transferred to the second compressor 9.

In the channel of the refrigerant between the first compressor 1 and thefirst outdoor heat exchanger portion 2 a and the channel of therefrigerant between the first outdoor heat exchanger portion 2 a and thesecond compressor 9, there are provided a switch 10 a and a switch 10 bwhich are opened in the cooling operation to allow the refrigerant topass therethrough and closed in the heating operation to block therefrigerant, respectively.

In the channel of the refrigerant between the first compressor 1 and thesecond compressor 9, there is provided a switch 7 c which is closed inthe cooling operation to block the refrigerant and allows therefrigerant to pass therethrough in the heating operation.

At an inlet of the refrigerant of the expander 3, there is provided afirst foreign particle trap 11 for trapping foreign particles containedin the refrigerant that flows into the expander 3.

At an inlet of the refrigerant of the second compressor 9, there isprovided a second foreign particle trap 12 for trapping foreignparticles contained in the refrigerant that flows into the secondcompressor 9.

Each of the first foreign particle trap 11 and the second foreignparticle trap 12 includes a strainer made of a coarse metal mesh. Thecoarseness of the metal mesh determines the size of the smallest foreignparticles to be trapped.

The size of the smallest foreign particles to be trapped by the firstforeign particle trap 11 is set to be smaller than the largest gap in anexpansion chamber of the expander 3.

The size of the smallest foreign particles to be trapped by the secondforeign particle trap 12 is set to be smaller than the largest gap in acompression chamber of the second compressor 9.

The size of the smallest foreign particles to be trapped by each of thefirst foreign particle trap 11 and the second foreign particle trap 12is 0.5 mm. Therefore, a pressure loss caused by each of the firstforeign particle trap 11 and the second foreign particle trap 12 isdecreased, to thereby suppress a reduction of power to be recovered.

At an inlet of the refrigerant of the first compressor 1, there isprovided an accumulator 13 for accumulating the refrigerant beforeflowing into the first compressor 1.

In the channel of the refrigerant among the outdoor heat exchanger 2,the second compressor 9, the indoor heat exchanger 4, and theaccumulator 13, there is provided a first four-way valve 14. Valves inthe first four-way valve 14 are switched so that the refrigerant isallowed to flow from the second compressor 9 to the second outdoor heatexchanger portion 2 b and the refrigerant is allowed to flow from theindoor heat exchanger 4 to the accumulator 13 in the cooling operation,and the refrigerant is allowed to flow from the second compressor 9 anda check valve 15 bypassing the second compressor 9 and the secondforeign particle trap 12 to the indoor heat exchanger 4 and therefrigerant is allowed to flow from the outdoor heat exchanger 2 to theaccumulator 13 in the heating operation. It should be noted that thecheck valve 15 may be included in the second compressor 9.

In the channel of the refrigerant among the outdoor heat exchanger 2,the expander 3, and the indoor heat exchanger 4, there is provided asecond four-way valve 16. Valves in the second four-way valve 16 areswitched so that the refrigerant is allowed to flow from the secondoutdoor heat exchanger portion 2 b through the expander 3 to the indoorheat exchanger 4 in the cooling operation, and the refrigerant isallowed to flow from the indoor heat exchanger 4 through the expander 3to the outdoor heat exchanger 2 in the heating operation.

The first four-way valve 14 and the second four-way valve 16 serve toallow the refrigerant to pass through the expander 3 and the secondcompressor 9 in the same direction regardless of the cooling operationor the heating operation.

In the channel of the refrigerant between the outdoor heat exchanger 2and the indoor heat exchanger 4, there are provided a bypass circuit 17for bypassing the second four-way valve 16, the expander 3, and theon-off valve 6, and a bypass valve 18 for adjusting the flow rate of therefrigerant passing through the bypass circuit 17.

In the channel of the refrigerant between the second four-way valve 16and the first foreign particle trap 11, there is provided apre-expansion valve 19 for adjusting the flow rate of the refrigerantmoving from the second four-way valve 16 to the first foreign particletrap 11.

The bypass valve 18 and the pre-expansion valve 19 are adjusted so thatthe flow rate of the refrigerant passing through the second compressor 9and the sum of the flow rates of the refrigerant passing through theexpander 3 and the bypass circuit 17 are equal.

This way, a pressure on the high-pressure side may be increased to adesirable pressure to be adjusted, and further the power generated inthe expander 3 may be recovered. Therefore, the refrigerating cycle maybe maintained in a highly efficient state.

It should be noted that, without limiting to adjusting the bypass valve18 and the pre-expansion valve 19, any other method may be used toadjust the flow rate of the refrigerant passing through the secondcompressor 9 and the flow rates of the refrigerant passing through theexpander 3 and the bypass circuit 17 to be equal.

At an outlet of the refrigerant of the first compressor 1, there isprovided a pressure sensor 20 a for measuring a pressure of therefrigerant that flows out of the first compressor 1. At the inlet ofthe refrigerant of the expander 3, there is provided a pressure sensor20 b for measuring the pressure of the refrigerant that flows into theexpander 3. At an outlet of the refrigerant of the on-off valve 6, thereis provided a pressure sensor 20 c for measuring the pressure of therefrigerant that flows out of the on-off valve 6.

It should be noted that, without limiting to those positions, thepressure sensor 20 a, the pressure sensor 20 b, and the pressure sensor20 c may be located at any positions as long as the pressure of therefrigerant that flows out of the first compressor 1, the pressure ofthe refrigerant that flows into the expander 3, and the pressure of therefrigerant that flows out of the on-off valve 6 may be measured,respectively.

Further, each of the pressure sensor 20 a, the pressure sensor 20 b, andthe pressure sensor 20 c may be a temperature sensor for measuring atemperature of the refrigerant as long as the pressure may be estimated.

The pressure sensor 20 a, the pressure sensor 20 b, and the pressuresensor 20 c are connected to a controller 21. The controller 21 controlsthe opening and closing of the on-off valve 6, the bypass valve 18, andthe pre-expansion valve 19 based on values of the pressure of therefrigerant measured by the pressure sensor 20 a, the pressure sensor 20b, and the pressure sensor 20 c.

The controller 21 includes judging means (not shown) for judging, afterthe on-off valve 6 is fully opened, whether or not the expander 3 isstarted up, storage means (not shown) for storing the number of times itis judged that the expander 3 is not started up, and display means (notshown) for displaying, when the number of times stored in the storagemeans has reached a predetermined number of times, a notification thatthe expander 3 has failed.

The first compressor 1, the outdoor heat exchanger 2, the expander 3,the drive shaft 5, the on-off valve 6, the switch 7 a, the switch 7 b,the switch 7 c, the second compressor 9, the switch 10 a, the switch 10b, the first foreign particle trap 11, the second foreign particle trap12, the accumulator 13, the first four-way valve 14, the check valve 15,the second four-way valve 16, the bypass circuit 17, the bypass valve18, the pre-expansion valve 19, the pressure sensor 20 a, the pressuresensor 20 b, the pressure sensor 20 c, and the controller 21 constitutean outdoor unit 22.

The first indoor heat exchanger portion 4 a and the indoor expansionvalve 8 a constitute an indoor unit 23 a, and the second indoor heatexchanger portion 4 b and the indoor expansion valve 8 b constitute anindoor unit 23 b.

The outdoor unit 22 is connected to one end of each of a liquid mainpipe 24 and a gas main pipe 25, the other end of the liquid main pipe 24is connected to one end of each of a liquid branch pipe 26 a and aliquid branch pipe 26 b, and the other end of the gas main pipe 25 isconnected to one end of each of a gas branch pipe 27 a and a gas branchpipe 27 b.

The other end of the liquid branch pipe 26 a is connected to the indoorexpansion valve 8 a, and the other end of the liquid branch pipe 26 b isconnected to the indoor expansion valve 8 b.

The other end of the gas branch pipe 27 a is connected to the firstindoor heat exchanger portion 4 a, and the other end of the gas branchpipe 27 b is connected to the second indoor heat exchanger portion 4 b.

The first compressor 1 is connected to a motor (not shown). The firstcompressor 1 is driven by the motor to operate.

The expander 3 and the second compressor 9 are of a positivedisplacement type, specifically, a scroll type.

It should be noted that, without limiting to the scroll type, theexpander 3 and the second compressor 9 may be of any other positivedisplacement type.

The expander 3 and the second compressor 9 do not have a motor thatgenerates heat.

Further, the expander 3 and the second compressor 9 have substantiallyequal bearing loads, and hence the expander 3 and the second compressor9 cause small loss.

Therefore, there is no need to use the refrigerant to cool inside theexpander 3 and the second compressor 9, and hence decrease ofrefrigerator oil that occurs when the refrigerant cools the expander 3and the second compressor 9 may be suppressed.

As a result, reliability of the expander 3 and the second compressor 9may be increased.

Further, reduction in heat transfer performance of the heat exchangerdue to the decrease of the refrigerator oil may be suppressed.

The first outdoor heat exchanger portion 2 a and the second outdoor heatexchanger portion 2 b may be connected via the channel of therefrigerant in series in the cooling operation to improve the heattransfer performance for radiating heat, and in parallel in the heatingoperation to reduce the pressure loss.

Next, operation of the air conditioner according to this embodiment isdescribed.

In the cooling operation, the refrigerant of low pressure first flowsinto the first compressor 1 and is compressed to become high intemperature and medium in pressure.

After flowing out of the first compressor 1, the refrigerant passesthrough the switch 10 a and flows into the first outdoor heat exchangerportion 2 a of the outdoor heat exchanger 2.

After radiating heat to transfer the heat to outdoor air in the firstoutdoor heat exchanger portion 2 a, the refrigerant becomes low intemperature and medium in pressure.

After flowing out of the first outdoor heat exchanger portion 2 a, therefrigerant flows into the second compressor 9 and is compressed tobecome high in temperature and high in pressure.

After flowing out of the second compressor 9, the refrigerant passesthrough the first four-way valve 14 and flows into the second outdoorheat exchanger portion 2 b, in which the refrigerant radiates heat totransfer the heat to outdoor air and become low in temperature and highin pressure.

After flowing out of the second outdoor heat exchanger portion 2 b, therefrigerant is branched to a path that leads to the second four-wayvalve 16 and a path that leads to the bypass valve 18.

The refrigerant that has passed through the second four-way valve 16passes through the pre-expansion valve 19 and the first foreign particletrap 11, flows into the expander 3, and is decompressed to become low inpressure and take on a state of low dryness.

At this time, power is generated in the expander 3 upon thedecompression of the refrigerant. The power is recovered by the driveshaft 5 and transferred to the second compressor 9 to be used by thesecond compressor 9 to compress the refrigerant.

After flowing out of the expander 3, the refrigerant passes through theon-off valve 6 and the second four-way valve 16, and then joins therefrigerant that has been directed to the bypass valve 18 and has passedthrough the bypass circuit 17. The refrigerant flows out of the outdoorunit 22, passes through the liquid main pipe 24 and then the liquidbranch pipe 26 a and the liquid branch pipe 26 b, and flows into theindoor unit 23 a and the indoor unit 23 b, in which the refrigerantflows into the indoor expansion valve 8 a and the indoor expansion valve8 b.

In the indoor expansion valve 8 a and the indoor expansion valve 8 b,the refrigerant is further decompressed.

After flowing out of the indoor expansion valve 8 a and the indoorexpansion valve 8 b, the refrigerant absorbs heat from indoor air and isevaporated in the first indoor heat exchanger portion 4 a and the secondindoor heat exchanger portion 4 b to take on a state of high drynesswhile maintaining low pressure.

This way, indoor air is cooled.

After flowing out of the first indoor heat exchanger portion 4 a and thesecond indoor heat exchanger portion 4 b, the refrigerant flows out ofthe indoor unit 23 a and the indoor unit 23 b, passes through the gasbranch pipe 27 a and the gas branch pipe 27 b and then the gas main pipe25, and flows into the outdoor unit 22, in which the refrigerant passesthrough the first four-way valve 14 and flows into the accumulator 13and again into the first compressor 1.

The above-mentioned operation is repeated to transfer heat of indoor airto outdoor air and thereby cool the room.

In the heating operation, the refrigerant of low pressure first flowsinto the first compressor 1 and is compressed to become high intemperature and high in pressure.

After flowing out of the first compressor 1, the refrigerant passesthrough the switch 7 c, the check valve 15, and the first four-way valve14.

At this time, part of the refrigerant, which has passed through theswitch 7 c, passes through the second compressor 9 and then joins therefrigerant that has passed through the check valve 15 to flow into thefirst four-way valve 14.

After passing through the first four-way valve 14, the refrigerant flowsout of the outdoor unit 22, passes through the gas main pipe 25 and thenthe gas branch pipe 27 a and the gas branch pipe 27 b, and flows intothe indoor unit 23 a and the indoor unit 23 b, in which the refrigerantflows into the first indoor heat exchanger portion 4 a and the secondindoor heat exchanger portion 4 b of the indoor heat exchanger 4. In thefirst indoor heat exchanger portion 4 a and the second indoor heatexchanger portion 4 b, the refrigerant radiates heat to transfer theheat to indoor air to become low in temperature and high in pressure.

After flowing out of the first indoor heat exchanger portion 4 a and thesecond indoor heat exchanger portion 4 b, the refrigerant isdecompressed in the indoor expansion valve 8 a and the indoor expansionvalve 8 b.

After flowing out of the indoor expansion valve 8 a and the indoorexpansion valve 8 b, the refrigerant flows out of the indoor unit 23 aand the indoor unit 23 b, passes through the liquid branch pipe 26 a andthe liquid branch pipe 26 b and then the liquid main pipe 24, flows intothe outdoor unit 22, and is branched to a path that leads to the secondfour-way valve 16 and a path that leads to the bypass valve 18.

The refrigerant that has passed through the second four-way valve 16passes through the pre-expansion valve 19 and the first foreign particletrap 11, flows into the expander 3, and is decompressed to become low inpressure and take on the state of low dryness.

At this time, power is generated in the expander 3 upon thedecompression of the refrigerant. The power is recovered by the driveshaft 5, transferred to the second compressor 9, and used by the secondcompressor 9 to compress the refrigerant.

After flowing out of the expander 3, the refrigerant passes through theon-off valve 6 and the second four-way valve 16, and then joins therefrigerant that has been directed to the bypass valve 18 and has passedthe bypass circuit 17. The refrigerant is branched again to flow intothe first outdoor heat exchanger portion 2 a and the second outdoor heatexchanger portion 2 b.

In the first outdoor heat exchanger portion 2 a and the second outdoorheat exchanger portion 2 b, the refrigerant absorbs heat from outdoorair and is evaporated to take on a state of high dryness whilemaintaining low pressure.

After flowing out of the first outdoor heat exchanger portion 2 a andthe second outdoor heat exchanger portion 2 b, the refrigerant joinsagain, passes through the first four-way valve 14, and flows into theaccumulator 13 and again into the first compressor 1.

The above-mentioned operation is repeated to transfer heat of outdoorair to indoor air and thereby heat the room.

The air conditioner is used as a multi-system air conditioner for abuilding and adapted to increase an operation efficiency in a mildcooling season in which a cooling load is not large in order to increasean annual operation efficiency.

Therefore, the expander 3, the second compressor 9, the outdoor heatexchanger 2, and the indoor heat exchanger 4 are designed to be best forthe mild cooling season. In the heating operation, it is moreadvantageous in control for the refrigerant not to pass through theexpander 3 and the second compressor 9.

However, when the refrigerant does not pass through the expander 3 andthe second compressor 9 in the heating operation, the refrigerant dwellsin the expander 3 and the second compressor 9. As a result, when theexpander 3 and the second compressor 9 are started up, the expander 3and the second compressor 9 may be damaged due to poor lubrication.

Therefore, the refrigerant is allowed to pass through the expander 3 andthe second compressor 9 also in the heating operation.

It should be noted that the second compressor 9 operates to such anextent as not to compress the refrigerant.

Next, power to be transferred from the expander 3 to the secondcompressor 9 of the air conditioner according to this embodiment isdescribed.

FIG. 3( a) is a schematic diagram illustrating a breakdown of the powertransferred from the expander 3 to the second compressor 9 in a steadystate, and FIG. 3( b) is a schematic diagram illustrating a breakdown ofthe power transferred from the expander 3 to the second compressor 9during activation.

Both in the steady state and during the activation, the power to beultimately recovered is power obtained by subtracting the loss caused bythe expander 3 and the loss caused by the second compressor 9 from thepower received by the expander 3 from the dynamic pressure of therefrigerant.

However, in comparison to the steady state, the loss generated by theexpander 3 and the loss generated by the second compressor 9 becomelarger during the activation, and hence less power is ultimatelyrecovered.

This is because, soon after the activation of the expander 3 when thenumber of rotations is equal to or less than a predetermined number ofrotations, a friction coefficient of the bearing is increased toincrease the friction loss.

Further, when the expander 3 is in an inactive state, static frictionlarger than dynamic friction occurs in bearings of the expander 3 andthe second compressor 9 to further increase the loss caused by theexpander 3 and the loss caused by the second compressor 9.

Further, when the air conditioner has been in an inactive state for along time, the refrigerator oil in the expander 3 and the secondcompressor 9 is increased in viscosity due to low temperature. When theair conditioner is to be started up to start up the expander 3 from thisstate, the loss caused by the expander 3 and the loss caused by thesecond compressor 9 are further increased.

Further, soon after the air conditioner is manufactured and shipped, theoperation time is too short for slide members of the expander 3 and thesecond compressor 9 to fit well, to thereby cause large friction andfurther increase the loss caused by the expander 3 and the loss causedby the second compressor 9.

Next, operation of the expander 3 during the activation, that is, soonafter the on-off valve 6 is fully opened from a fully closed state, isdescribed.

FIG. 4( a) is a diagram illustrating the pressure of the refrigerant, avolume of the refrigerant, and a mass of the refrigerant in the steadystate of the expander 3, and FIG. 4( b) is a diagram illustrating thepressure of the refrigerant, the volume of the refrigerant, and the massof the refrigerant during the activation of the expander 3.

In the steady state, the pressure of the refrigerant in the expansionchamber of the expander 3 is equal to an inlet pressure that is thepressure at the inlet of the refrigerant of the expander 3 at a startpoint of an expansion process, decreases in the course of the expansionprocess from the start point to an end point of the expansion process,and becomes equal to an outlet pressure that is the pressure at anoutlet of the refrigerant of the expander 3 at the end point of theexpansion process.

The volume of the refrigerant in the expansion chamber of the expander 3increases from the start point to the end point of the expansionprocess.

The mass of the refrigerant in the expansion chamber of the expander 3does not change between the start point and the end point of theexpansion process.

In contrast, during the activation, that is, soon after the on-off valve6 is fully opened from the fully closed state, the pressure of therefrigerant in the expansion chamber of the expander 3 does not changebetween the start point and the end point of the expansion process. Onthe downstream side of the end point, the pressure changesdiscontinuously to be decreased and become equal to the pressure of therefrigerant measured by the pressure sensor 20 c.

The volume of the refrigerant in the expansion chamber of the expander 3increases as in the steady state from the start point to the end pointof the expansion process.

The mass of the refrigerant in the expansion chamber of the expander 3increases from the start point to the end point of the expansionprocess.

Therefore, the circulating volume of the refrigerant during the periodin which the expander 3 is started up and the expander 3 is rotated onceis larger than the circulating volume of the refrigerant in the steadystate to give larger rotation power.

Further, the interface area between the expansion chamber and spaceafter the expansion process is large before and after the endpoint ofthe expansion process, and a pressure difference between before andafter the end point of the expansion process is larger than the pressuredifference in the steady state soon after the on-off valve 6 is fullyopened from the fully closed state, to thereby give large recoveredpower that is determined by the area and the pressure.

As described above, soon after the on-off valve 6 is fully opened fromthe fully closed state, the expander 3 may obtain the large recoveredpower.

Therefore, even when the loss caused by the expander 3 and the losscaused by the second compressor 9 are large, the expander 3 may bestarted up.

Further, the on-off valve 6 is fully closed from when the firstcompressor 1 is started up until when the pressure of the refrigerant inthe expander 3 becomes a critical pressure or higher, and hence thehigh-pressure refrigerant reduces the viscosity of the refrigerator oilin the expander 3 and the second compressor 9.

This way, the loss caused by the expander 3 and the loss caused by thesecond compressor 9 soon after the on-off valve 6 is fully opened may bedecreased, and hence the expander 3 may obtain the large recoveredpower.

Next, start-up operation of the air conditioner according to thisembodiment is described.

FIG. 5 is a flow chart illustrating the start-up operation of the airconditioner of FIGS. 1 and 2.

When the air conditioner is started up (Step S1), it is judged which ofcooling operation and heating operation the requested operation is (StepS2).

When it is judged in Step S2 that the heating operation is requested,the heating operation is started (Step S3).

On the other hand, when it is judged in Step S2 that the coolingoperation is requested, the cooling operation is started (Step S4).

When the cooling operation is started, a first cooling circuit is set,in which the switch 7 a, the switch 7 b, and the switch 7 c are closed,the switch 10 a and the switch 10 b are opened, valves in the firstfour-way valve 14 are switched so that the refrigerant is allowed toflow from the second compressor 9 to the second outdoor heat exchangerportion 2 b and the refrigerant is allowed to flow from the indoor heatexchanger 4 to the accumulator 13, and valves in the second four-wayvalve 16 are switched so that the refrigerant is allowed to flow fromthe second outdoor heat exchanger portion 2 b through the expander 3 tothe indoor heat exchanger 4 (Step S5).

Then, the on-off valve 6 is fully closed and the pre-expansion valve 19is fully opened (Step S6), and other devices are put into a firstinitial cooling setting that is an initial state of the coolingoperation (Step S7) so that the air conditioner enters a first start-upmode (Step S8).

When the air conditioner enters the first start-up mode, first, thefirst compressor 1 is started up (Step S9), the pressure sensor 20 bmeasures the pressure of the refrigerant at the inlet of the expander 3,the pressure sensor 20 c measures the pressure of the refrigerant at theoutlet of the on-off valve 6, and the controller 21 calculates adifference between the pressure of the refrigerant at the inlet of theexpander 3 and the pressure of the refrigerant at the outlet of theon-off valve 6 (Step S10).

Then, the controller 21 judges whether a predetermined period Ta haselapsed since the first compressor 1 is started up (Step S11).

The predetermined period Ta is preset in a range of from 10 seconds to60 seconds.

It should be noted that the predetermined period Ta is not limited tothe time range.

When the controller 21 judges in Step S11 that the predetermined periodTa has not elapsed since the first compressor 1 is started up, theprocess returns to Step S10.

On the other hand, when the controller 21 judges in Step S11 that thepredetermined period Ta has elapsed, it is judged whether the pressureof the refrigerant at the inlet of the expander 3 is equal to or higherthan the critical pressure and the difference between the pressure ofthe refrigerant at the inlet of the expander 3 and the pressure of therefrigerant at the outlet of the on-off valve 6 is equal to or largerthan a predetermined pressure Pa (Step S12).

The predetermined pressure Pa is preset in a range of from 2.5 MPa to 5MPa.

When the controller 21 judges in Step S12 that the pressure of therefrigerant at the inlet of the expander 3 is not equal to or higherthan the critical pressure or that the difference between the pressureof the refrigerant at the inlet of the expander 3 and the pressure ofthe refrigerant at the outlet of the on-off valve 6 is not equal to orlarger than the predetermined pressure Pa, a degree of opening of thebypass valve 18 is reduced (Step S13) and the process returns to StepS10.

On the other hand, when the controller 21 judges in Step S12 that thepressure of the refrigerant at the inlet of the expander 3 is equal toor higher than the critical pressure and that the difference between thepressure of the refrigerant at the inlet of the expander 3 and thepressure of the refrigerant at the outlet of the on-off valve 6 is equalto or larger than the predetermined pressure Pa, the on-off valve 6 isfully opened (Step S14).

Then, the controller 21 judges whether a predetermined period Tb haselapsed since the on-off valve 6 is fully opened (Step S15).

The predetermined period Tb is shorter than the predetermined period Taof Step S11 and preset in a range of from 5 seconds to 30 seconds.

It should be noted that the predetermined period Tb is not limited tothe time range.

When the controller 21 judges in Step S15 that the predetermined periodTb has not elapsed since the on-off valve 6 is fully opened, Step S15 isrepeated.

On the other hand, when the controller 21 judges in Step S15 that thepredetermined period Tb has elapsed, the pressure sensor 20 a measuresthe pressure of the refrigerant at the outlet of the first compressor 1,the pressure sensor 20 b measures the pressure of the refrigerant at theinlet of the expander 3, and the controller 21 calculates a differencebetween the pressure of the refrigerant at the inlet of the expander 3and the pressure of the refrigerant at the outlet of the firstcompressor 1 (Step S16).

Then, the controller 21 judges whether the difference between thepressure of the refrigerant at the inlet of the expander 3 and thepressure of the refrigerant at the outlet of the first compressor 1 isequal to or larger than a predetermined pressure Pb (Step S17).

The predetermined pressure Pb is preset in a range of from 0 MPa to 0.5MPa.

It should be noted that the predetermined pressure Pb is not limited tothe pressure range.

When the controller 21 judges in Step S17 that the difference betweenthe pressure of the refrigerant at the inlet of the expander 3 and thepressure of the refrigerant at the outlet of the first compressor 1 isequal to or larger than the predetermined pressure Pb, the judging meansjudges that the expander 3 has successfully started up, the airconditioner exits the first start-up mode, and first steady control in asteady state is performed (Step S18).

On the other hand, when the controller 21 judges in Step S17 that thedifference between the pressure of the refrigerant at the inlet of theexpander 3 and the pressure of the refrigerant at the outlet of thefirst compressor 1 is not equal to or larger than the predeterminedpressure Pb, the judging means judges that the activation of theexpander 3 has failed, and the air conditioner enters a backup mode(Step S19).

When the air conditioner enters the backup mode, the storage means addsone to the number of times the activation failed stored therein (StepS20), and further judges whether the number of times the activationfailed is the predetermined number of times (Step S21).

The predetermined number of times is preset in a range of from 5 to 10.

It should be noted that the predetermined number of times is not limitedto the number range.

When the controller 21 judges in Step S21 that the number of times theactivation failed is less than the predetermined number of times, theprocess returns to Step S5.

On the other hand, when the controller 21 judges in Step S21 that thenumber of times the activation failed has reached the predeterminednumber of times, the expander 3 or the second compressor 9 is regardedas having failed, and the air conditioner starts backup control (StepS22).

In the backup control, first, the first compressor 1 is stopped (StepS23), the display means of the controller 21 displays a notificationthat the expander 3 or the second compressor 9 has failed (Step S24) tonotify the manager or the user of the failure.

Then, a second cooling circuit is set so that the refrigerant does notflow into the expander 3 and the second compressor 9 (Step S25), inwhich the on-off valve 6 is fully closed, the pre-expansion valve 19 isclosed, and the bypass valve 18 is opened so that the refrigerant doesnot pass through the expander 3 and the second compressor 9, and otheractuators are put into a second initial cooling setting that is a statebefore cooling is started (Step S26).

The air conditioner enters a second start-up mode in which the expander3 is not started up (Step S27), and the first compressor 1 is started upwithout operating the expander 3 to perform steady operation in thesteady state (Step S28), so that the cooling operation in which therefrigerant is circulated continues as illustrated in a refrigerantcircuit diagram of FIG. 6.

In this case, if, for example, the expander 3 or the second compressor 9has failed, the refrigerant does not pass through the expander 3 and thesecond compressor 9 so as to prevent the first compressor 1, the indoorexpansion valve 8 a, the indoor expansion valve 8 b, and the like frombeing damaged.

Further, if, for example, the expander 3 or the second compressor 9 hasfailed, the cooling operation may be continued.

As described above, according to the air conditioner of this embodiment,even if large power is required to start up the expander 3, the on-offvalve 6 is fully opened after the first compressor 1 is started up andthe pressure of the refrigerant in the expander 3 is increased, tothereby increase the refrigerant that passes through the on-off valve 6.As a result, the expander 3 may be started up by the dynamic pressure ofthe refrigerant.

Further, even if the refrigerator oil in the expander 3 and the secondcompressor 9 is increased in viscosity due to low temperature, when thepressure of the refrigerant at the inlet of the expander 3 is equal toor higher than the critical pressure, the on-off valve 6 is fully openedto allow the refrigerant to pass through the on-off valve 6. Therefrigerant of the critical pressure or higher acts on the refrigeratoroil to decrease the viscosity of the refrigerator oil. Therefore, thelosses caused by the expander 3 and the second compressor 9 may bedecreased.

Further, when the difference between the pressure of the refrigerant atthe inlet of the refrigerant of the expander 3 and the pressure of therefrigerant at the outlet thereof is equal to or larger than thepredetermined pressure, the on-off valve 6 is fully opened to allow therefrigerant to pass through the on-off valve 6. Therefore, the expander3 may be started up by the high dynamic pressure of the refrigerant.

Further, the air conditioner of this embodiment includes the judgingmeans for judging whether or not the expander 3 is started up after theon-off valve 6 is fully opened, the storage means for storing the numberof times the judging means judges that the expander 3 is not started up,and a display device for displaying a notification that the expander 3and the second compressor 9 have failed when the number of times storedin the storage means has reached the predetermined number of times.Therefore, the manager or the user may easily notice that the expander 3and the second compressor 9 have failed.

In the channel of the refrigerant between the outdoor heat exchanger 2and the indoor heat exchanger 4, there are provided the bypass circuit17 connected in parallel to the expander 3 and the on-off valve 6 thatare connected in series, and the bypass valve 18 for adjusting the flowrate of the refrigerant passing through the bypass circuit 17. When thenumber of times stored in the storage means has reached thepredetermined number of times, the refrigerant passes through the bypasscircuit 17. Therefore, when the expander 3 or the second compressor 9fails and hence the expander 3 and the second compressor 9 do not work,the refrigerant may circulate through the channel of the refrigerantbetween the outdoor heat exchanger 2 and the indoor heat exchanger 4.

Further, the refrigerant movement control means is the on-off valve 6that is fully closed to restrict the movement of the refrigerant fromthe expander 3 to the indoor heat exchanger 4 in the cooling operationand is fully opened to control the flow rate of the refrigerant thatmoves from the expander 3 to the indoor heat exchanger 4 in the coolingoperation. Therefore, the movement of the refrigerant from the expander3 to the indoor heat exchanger 4 may be controlled with a simpleconfiguration.

Further, in the channel of the refrigerant between the first compressor1 and the outdoor heat exchanger 2, there is provided the secondcompressor 9, and power is transferred from the expander 3 via the driveshaft 5 to the second compressor 9 in the cooling operation. Therefore,the power that is generated when the refrigerant is decompressed by theexpander 3 may be used by the second compressor 9, so that the airconditioner may be increased in efficiency.

Further, at the inlet of the refrigerant of the expander 3, there isprovided the first foreign particle trap 11 for trapping the foreignparticles entering the expander 3. The size of the smallest foreignparticles to be trapped by the first foreign particle trap 11 is smallerthan the largest gap in the expansion chamber of the expander 3.Therefore, the foreign particles may be prevented from entering theexpander 3 and causing the expander 3 to fail.

Further, at the inlet of the refrigerant of the second compressor 9,there is provided the second foreign particle trap 12 for trapping theforeign particles entering the second compressor 9. The size of thesmallest foreign particles to be trapped by the second foreign particletrap 12 is smaller than the largest gap in the compression chamber ofthe second compressor 9. Therefore, the foreign particles may beprevented from entering the second compressor 9 and causing the secondcompressor 9 to fail.

The refrigerant is carbon dioxide and hence may reduce ozone depletionand global warming compared to the conventional fluorocarbonrefrigerant.

It should be noted that, in this embodiment, the indoor heat exchanger 4has been described to include the first indoor heat exchanger portion 4a and the second indoor heat exchanger portion 4 b. However, it shouldbe understood that the present invention is not limited thereto, and theindoor heat exchanger 4 may include one indoor heat exchanger portion,or the indoor heat exchanger 4 may include three or more indoor heatexchanger portions.

Further, the air conditioner has been described to have theconfiguration in which the indoor expansion valve 8 a is connected tothe first indoor heat exchanger portion 4 a and the indoor expansionvalve 8 b is connected to the second indoor heat exchanger portion 4 b.However, the air conditioner may have a configuration in which a singleindoor expansion valve is connected to the first indoor heat exchangerportion 4 a and the second indoor heat exchanger portion 4 b, oralternatively, the air conditioner may have a configuration in which anoutdoor expansion valve is provided to the outdoor unit 22.

Further, the on-off valve 6 has been described to restrict the movementof the refrigerant from the expander 3 to the downstream side when fullyclosed and to control the flow rate of the refrigerant moving from theexpander 3 to the downstream side when fully opened. However, it shouldbe understood that the present invention is not limited thereto, and aflow regulating valve that is fully closed or nearly fully closed torestrict the movement of the refrigerant from the expander 3 to thedownstream side and is adjusted in degree of opening to control the flowrate of the refrigerant moving from the expander 3 to the downstreamside may be used.

Further, the second compressor 9 has been described to operate only onthe rotation power transferred from the expander 3. However, it shouldbe understood that the present invention is not limited thereto, and thesecond compressor 9 may operate, for example, on the rotation powertransferred from the expander 3 as well as the rotation power from amotor.

Further, whether or not to start up the expander 3 has been judged basedon the difference between the pressure of the refrigerant at the inletof the refrigerant of the expander 3 and the pressure of the refrigerantat the outlet of the refrigerant of the on-off valve 6. However, itshould be understood that the present invention is not limited thereto,and whether or not to start up the expander 3 may be judged byinstalling a tachometer or a vibrometer to the expander 3 and the secondcompressor 9 or by measuring the temperature of the refrigerant at theoutlet of the refrigerant of or inside the second compressor 9.

Second Embodiment

FIG. 7 is a refrigerant circuit diagram of a water heater according to asecond embodiment of the present invention.

The water heater, which is a refrigerating cycle apparatus according tothis embodiment, includes a compressor 28 for compressing a refrigerant,a radiator 29 for radiating heat of the refrigerant compressed by thecompressor 28 to heat water, an expander 30 for decompressing therefrigerant that has passed through the radiator 29, an evaporator 31 inwhich the refrigerant that has passed through the expander 30 absorbsheat and is evaporated, and a power generator 32 which is connected tothe expander 30 and serves as a power recovery device for recoveringpower that is generated when the refrigerant is decompressed by theexpander 30.

In a channel of the refrigerant between the expander 30 and theevaporator 31, there is provided an opening regulating valve 33 whichserves as refrigerant movement control means that is fully closed ornearly fully closed to restrict the movement of the refrigerant from theexpander 30 to the evaporator 31 and is adjusted in degree of opening tocontrol the flow rate of the refrigerant moving from the expander 30 tothe evaporator 31.

At an inlet of the refrigerant of the compressor 28, there is provided apressure sensor 34 a for measuring a pressure of the refrigerant thatflows into the compressor 28. At an outlet of the refrigerant of thecompressor 28, there is provided a pressure sensor 34 b for measuringthe pressure of the refrigerant that flows out of the compressor 28.

The pressure sensor 34 a and the pressure sensor 34 b are connected to acontroller 35. The controller 35 adjusts the degree of opening of theopening regulating valve 33 based on values of the pressure of therefrigerant measured by the pressure sensor 34 a and the pressure sensor34 b.

The controller 35 includes judging means (not shown) for judging, afterthe degree of opening of the opening regulating valve 33 is increased,whether or not the expander 30 is started up, and storage means (notshown) for storing the number of times it is judged that the expander 30is not started up.

The refrigerant is made of carbon dioxide.

The radiator 29 includes water transportation means 36 for pumping waterinto the radiator 29 and a hot water supply tank 37 for storing waterthat has been heated by passing through the radiator 29.

The evaporator 31 includes a blower (not shown) for blowing on theevaporator 31.

Next, operation of the water heater according to this embodiment isdescribed.

First, the refrigerant of low temperature and low pressure flows intothe compressor 28 and is compressed to take on a state of hightemperature and high pressure.

After flowing out of the compressor 28, the refrigerant radiates heat inthe radiator 29 to take on a state of low temperature and high pressure.

At this time, the heat of the refrigerant is transferred to water viathe radiator 29 to heat the water.

After flowing out of the radiator 29, the refrigerant is decompressed inthe expander 30 to take on a state of low temperature and low pressure.

At this time, power that is generated when the refrigerant isdecompressed in the expander 30 is recovered by the power generator 32.

The power recovered from the power generator 32 is converted toelectrical energy and used by the compressor 28, the watertransportation means 36, and the blower.

After flowing out of the expander 30, the refrigerant absorbs heat inthe evaporator 31 and is evaporated to become low in pressure and changefrom a state of low dryness to a state of high dryness.

At this time, the blower blows on the evaporator 31 so that therefrigerant in the evaporator 31 may absorb the heat effectively.

After flowing out of the evaporator 31, the refrigerant flows into thecompressor 28 again.

Next, start-up operation of the water heater according to thisembodiment is described.

FIG. 8 is a flow chart illustrating the start-up operation of the waterheater of FIG. 7.

When the water heater is started up (Step S101), the opening regulatingvalve 33 is switched to a state of being fully opened or nearly fullyopened (Step S102).

Next, other devices are set to an initial operating state (Step S103),and the water heater enters a start-up mode to start up the compressor28 (Step S104).

Next, the pressure sensor 34 a and the pressure sensor 34 b measure thepressure of the refrigerant at the inlet of the compressor 28 and thepressure of the refrigerant at the outlet thereof, respectively, and thecontroller 35 calculates a difference between the pressure of therefrigerant at the inlet of the compressor 28 and the pressure of therefrigerant at the outlet thereof (Step S105).

Next, the controller 35 judges whether the difference between thepressure of the refrigerant at the inlet of the compressor 28 and thepressure of the refrigerant at the outlet thereof is equal to or largerthan the predetermined pressure (Step S106).

When the controller 35 judges in Step S106 that the difference betweenthe pressure of the refrigerant at the inlet of the compressor 28 andthe pressure of the refrigerant at the outlet thereof is smaller thanthe predetermined pressure, the process returns to Step S105.

On the other hand, when the controller 35 judges in Step S106 that thedifference between the pressure of the refrigerant at the inlet of thecompressor 28 and the pressure of the refrigerant at the outlet thereofis equal to or larger than the predetermined pressure, the degree ofopening of the opening regulating valve 33 is increased (Step S107).

Next, the controller 35 judges whether a predetermined period haselapsed since the degree of opening of the opening regulating valve 33is increased (Step S108).

When the controller 35 judges in Step S108 that the predetermined periodhas not elapsed since the degree of opening of the opening regulatingvalve 33 is increased, Step S108 is repeated.

On the other hand, when the controller 35 judges in Step S108 that thepredetermined period has elapsed, a voltage of the power generator 32 ismeasured (Step S109).

Then, the controller 35 judges whether the voltage of the powergenerator 32 is equal to or higher than a predetermined voltage (StepS110).

When the controller 35 judges in Step S110 that the voltage of the powergenerator 32 is equal to or higher than the predetermined voltage, thejudging means regards the activation of the expander 30 as a success,the water heater exits the start-up mode, and steady control in a steadystate is performed (Step S111).

On the other hand, when the controller 35 judges in Step S110 that thevoltage of the power generator 32 is lower than the predeterminedvoltage, the judging means regards the activation of the expander 30 asa failure, and the water heater enters a backup mode (Step S112).

When the water heater enters the backup mode, the storage means of thecontroller 35 adds one to the number of times the activation failedstored therein, and further judges whether the number of times theactivation failed is equal to or more than a predetermined number oftimes.

When the controller 35 judges that the number of times the activationfailed is less than the predetermined number of times, the processreturns to Step S102.

On the other hand, when the controller 35 judges that the number oftimes the activation failed has reached the predetermined number oftimes, the expander 30 or the power generator 32 is regarded as havingfailed, and the water heater starts backup control (Step S113).

In the backup control, the compressor 28 is stopped.

As described above, according to the water heater of this embodiment,the power generator 32 serves as the power recovery device, and thepower recovered by the power generator 32 may be converted to electricalenergy and used by the compressor 28, the water transportation means 36,and the blower.

Other effects are the same as those of the first embodiment.

Third Embodiment

FIG. 9 is a refrigerant circuit diagram of a water heater according to athird embodiment of the present invention.

The water heater according to this embodiment includes a firstcompressor 38 for compressing a refrigerant, a radiator 29 for radiatingheat of the refrigerant compressed by the first compressor 38, anexpander 30 for decompressing the refrigerant that has passed throughthe radiator 29, an evaporator 31 in which the refrigerant that haspassed through the expander 30 absorbs heat and is evaporated, a driveshaft 39 which is connected to the expander 30 and serves as a powerrecovery device for recovering power that is generated when therefrigerant is decompressed by the expander 30, and a second compressor40 which is connected to the drive shaft 39 and compresses therefrigerant that flows from the evaporator 31 into the first compressor38.

Other configurations are the same as those of the second embodiment.

Next, operation of the water heater according to this embodiment isdescribed.

The refrigerant of low temperature and low pressure first flows into thesecond compressor 40 and is compressed to take on a state of hightemperature and medium pressure.

After flowing out of the second compressor 40, the refrigerant flowsinto the first compressor 38 and is compressed to take on a state ofhigh temperature and high pressure.

After flowing out of the first compressor 38, the refrigerant radiatesheat in the radiator 29 to take on a state of low temperature and highpressure.

At this time, the heat of the refrigerant is transferred to water viathe radiator 29 to heat the water.

After flowing out of the radiator 29, the refrigerant is decompressed inthe expander 30 to take on a state of low temperature and low pressure.

At this time, power that is generated when the refrigerant isdecompressed in the expander 30 is recovered by the drive shaft 39 andused by the second compressor 40.

After flowing out of the expander 30, the refrigerant absorbs heat inthe evaporator 31 and is evaporated to become low in pressure and changefrom a state of low dryness to a state of high dryness.

At this time, the blower blows on the evaporator 31 so that therefrigerant in the evaporator 31 may absorb the heat effectively.

After flowing out of the evaporator 31, the refrigerant flows into thesecond compressor 40 again.

As described above, according to the water heater of this embodiment,the second compressor 40 is provided in a channel of the refrigerantbetween the evaporator 31 and the first compressor 38, and the driveshaft 39 is connected between the expander 30 and the second compressor40. Therefore, the power that is generated when the refrigerant isdecompressed in the expander 30 may be used by the second compressor 40.

Other effects are the same as those of the first embodiment.

1. A refrigerating cycle apparatus including: a first compressor forcompressing a refrigerant; a radiator for radiating heat of therefrigerant compressed by the first compressor; an expander fordecompressing the refrigerant that has passed through the radiator; anevaporator in which the refrigerant decompressed by the expander isevaporated; and a power recovery device which is connected to theexpander and recovers power that is generated when the refrigerant isdecompressed by the expander, the refrigerating cycle apparatuscomprising refrigerant movement control means which is provided in achannel of the refrigerant from the expander to the evaporator andcontrols a flow rate of the refrigerant moving from the expander to theevaporator, wherein, after the first compressor is started up toincrease a pressure of the refrigerant in the expander, the refrigerantmovement control means controls the flow rate of the refrigerant tostart up the expander by a dynamic pressure of the refrigerant in theexpander.
 2. A refrigerating cycle apparatus according to claim 1,wherein the refrigerant movement control means controls the flow rate ofthe refrigerant when the pressure of the refrigerant at an inlet of therefrigerant of the expander is equal to or higher than a criticalpressure.
 3. A refrigerating cycle apparatus according to claim 1,wherein the refrigerant movement control means controls the flow rate ofthe refrigerant when a difference between the pressure of therefrigerant at an inlet of the refrigerant of the refrigerant movementcontrol means and the pressure of the refrigerant at an outlet thereofis equal to or larger than 2.5 MPa.
 4. A refrigerating cycle apparatusaccording to claim 1, further comprising: judging means for judging,after the refrigerant movement control means controls the flow rate ofthe refrigerant, whether or not the expander is started up; storagemeans for storing a number of times the judging means judges that theexpander is not started up; and display means for displaying, when thenumber of times stored in the storage means has reached a predeterminednumber of times, a notification that the expander has failed.
 5. Arefrigerating cycle apparatus according to claim 4, further comprising,in a channel of the refrigerant between the radiator and the evaporator,a bypass circuit connected in parallel to the expander and therefrigerant movement control means that are connected in series, and abypass valve for adjusting the flow rate of the refrigerant passingthrough the bypass circuit, wherein the refrigerant is allowed to passthrough the bypass circuit when the number of times stored in thestorage means has reached the predetermined number of times.
 6. Arefrigerating cycle apparatus according to claim 1, wherein therefrigerant movement control means comprises an on-off valve that isfully closed to restrict movement of the refrigerant from the expanderto the evaporator and is fully opened to control the flow rate of therefrigerant moving from the expander to the evaporator.
 7. Arefrigerating cycle apparatus according to claim 1, wherein therefrigerant movement control means comprises a flow regulating valvethat is totally closed or nearly totally closed to restrict movement ofthe refrigerant from the expander to the evaporator and is adjusted indegree of opening to control the flow rate of the refrigerant movingfrom the expander to the evaporator.
 8. A refrigerating cycle apparatusaccording to claim 1, wherein the power recovery device comprises apower generator.
 9. A refrigerating cycle apparatus according to claim1, further comprising, in a channel of the refrigerant between the firstcompressor and the radiator, a second compressor for compressing therefrigerant, wherein the power recovery device comprises one drive shaftwhich is connected between the expander and the second compressor andtransfers the power from the expander to the second compressor.
 10. Arefrigerating cycle apparatus according to claim 1, further comprising,in a channel of the refrigerant between the first compressor and theevaporator, a second compressor for compressing the refrigerant, whereinthe power recovery device comprises one drive shaft which is connectedbetween the expander and the second compressor and transfers the powerfrom the expander to the second compressor.
 11. A refrigerating cycleapparatus according to claim 1, further comprising a first foreignparticle trap for trapping foreign particles entering the expander at aninlet of the refrigerant of the expander, wherein a size of a smallestone of the foreign particles to be trapped by the first foreign particletrap is smaller than a largest gap in an expansion chamber of theexpander.
 12. A refrigerating cycle apparatus according to claim 9,further comprising a second foreign particle trap for trapping foreignparticles entering the second compressor at an inlet of the refrigerantof the second compressor, wherein a size of a smallest one of theforeign particles to be trapped by the second foreign particle trap issmaller than a largest gap in a compression chamber of the secondcompressor.
 13. A refrigerating cycle apparatus according to claim 1,wherein the refrigerant comprises carbon dioxide.